Design of molecularly imprinted polymer materials relying on hydrophobic interactions

International audienc

Development of molecularly imprinted polymer for the selective recognition of the weakly interacting fenamiphos molecule

International audienceThe possible manufacture of Molecularly Imprinted Polymers (MIPs) under the conditions of weak interaction between the functional monomer and template molecule is addressed with the help of the case of the Fenamiphos organophosphorus insecticide. The choice of the functional monomer is addressed by investigating MIPs prepared by the surface imprinting technique using three very different types of monomers (methacrylic acid, 4-vinylpyridine and 2–(methacryloyloxyethyl)trimethylammonium chloride), a solid silica support grafted with 3-mercaptopropyltrimethoxysilane on its surface; ethylene glycol dimethacrylate as the cross-linker and acetonitrile as solvent. The prepared materials were characterized by IR, solid state 13C NMR, TGA, DLS, BET and TEM. Their performance as adsorbents were evaluated by modeling their experimental adsorption isotherms using the Langmuir–Volmer model. All MIPs show similar adsorbent performance although the functional monomers were quite different and the interactions with fenamiphos were weak. The latter were assessed by 1H and 31P NMR experiments in DMSO‑d6 solution. The adsorption process presented weakly exothermic and endothermic behavior onto molecular imprints and non-specific sites respectively. The selectivity for adsorption of fenamiphos with respect to its sulfone and sulfoxide metabolites was quite high

Choice of the functional monomer of molecularly imprinted polymers: Does it rely on strong acid-base or hydrogen bonding interactions?

International audienceThe choice of the functional monomer is a key point in the design of molecularly imprinted polymers (MIPs) because its directional interactions with template molecules are required to form molecular imprints acting as selective recognition sites for adsorption. Methacrylic acid (MAA) has very often been employed as a functional monomer for imprinting basic template molecules. Strong acid-base interactions lead to H+ transfer and weak hydrogen bonding between the products of the acid-base reaction. The weakly acidic acrylamide (AA) has shown stronger hydrogen-bonding interactions with histamine (HA) than MAA. Interactions between HA and the functional monomers have been investigated by means of 1H NMR spectroscopy yielding the stoichiometry and complexation constants of their complex species. Adsorption isotherms of HA to both MAA- and AA-based MIPs and their modeling showed a higher selective binding of HA to the AA-based MIP

Effect of cross-linking agents on the adsorption of histamine on molecularly imprinted polyacrylamide

International audienceThe ability of molecularly imprinted polymers (MIPs) prepared with flexible cross-linking agents for selective uptake of guest molecules is investigated. New polyacrylamide polymers had been synthesized for histamine (HA) extraction using solid supports based on MIPs immobilized on silica surface (SiO2). The MIPs were prepared via radical polymerization in acetonitrile and in the presence of azobisisobutyronitrile (AIBN) as initiator, using HA as a target molecule, acrylamide as a functional monomer and several cross-linking agents having alkyl spacers of various lengths: N,N’-methylenebisacrylamide (BA1), N,N’-ethylenebisacrylamide (BA2), N,N’-(butane-1,4-diyl)-bis(2-methacrylamide) (BA4) and N,N’-(hexane-1,6-diyl)-bis(2-methacrylamide) (BA6). All the prepared MIPs have a strong absorption capacity of HA compared to non-imprinted polyacrylamide (NIPs). MIP4 made with the BA4 cross-linker shows a higher selectivity for adsorption of HA than MIPs made with BA1, BA2 and BA6. Thus, the imprinting factor for adsorption from a 5 ppm HA solution was 2.5 for MIP4 against 1.4 to 1.6 for MIP1, MIP2 and MIP6. Langmuir–Volmer and Volmer models of the adsorption isotherms of MIPs and NIPs accurately fit the experimental data. They provide the characteristic parameters of the adsorption thermodynamic of the materials. The higher performance of MIP4 for selective adsorption of HA is mainly coming from a higher density of molecular imprints (1.4 µmol∙m−2 against 0.13–0.15 µmol∙m−2 for MIP1 and MIP2 and 0.4 µmol∙m−2 for MIP6) than a higher affinity of HA for the molecular imprints. The selectivity with respect to the tyramine and melamine interfering molecules is also higher for MIP4. As the main outcome, some moderate flexibility of the material is advantageous. Such flexibility allows for a reversible healing and re-opening of the molecular imprints as the HA guest is removed and back-adsorbed

The enhanced adsorption properties of molecular imprinted polymer material prepared using nitroxide-mediated Radical Deactivation Reversible Polymerization

International audienc